Process of recovering resinous by-products in the manufacture of wood pulp



E. H. FRENCH PROCESS OF REC OVERING RESINOUS BY-PRODUGTS IN THEMANUFACTURE OF WOOD PULP 2 Sheets-Sheet Nov. 27, 1928.

Filed Aug. 15, 1925 gnu Roz EdzJa/rcZHEwrwh Nov. 27, 1928. 1,693,586

. E. H. FRENCH PROCESS OF RECOVERING RESINOUS BY-PRODUCTS IN THEMANUFACTURE OF woon PULP Filed Aug. 15, 1925 2 Sheets-Sheet 2 gwuentozEda/c2 rdlifmnciv having iaaatat as uric.

EDWARD FRENCH, OF COLUMBUS, OHIO.

OF BECGVERING RESINOUS BY-JERODUGTS IN THE MANUFACTURE OF WWD PULP.

Application filed August 15, 1925. Serial No. 50,526.

In the manufacture of paper pulp produced fromresinous woods by theso-called sulphate process the wood is cleaned and chipped, placed in adigester where it is treated with a solution containing sodium sulphid(N a S) and caustic soda (N aOH) the wood being cooked with steamunderpressure in this liquor for a periodof several hours. Theturpentine of the mass is recov- 1o ered by distillation and thedigester blown,

w and converting the sulphates formed into the sulphids and carbonates.

During the described operation the pulping or black liquor referred toacquires a large quantity of resin and resin oils in the form allof'sodium resinate resulting from the combination of the caustic sodawith the abietic acid of the rosin of the wood. Many attempts have beenmade to recover the sodium resinates but, as far as I am aware, withoutcommercially satisfactory results. Among such attempts may be instanced(1) the c001 ing of the liquor thereby separating a portion of the resinand (2) the precipitating or salting out the resins by the use of ad- 39ditional alkali or salt, but by such methods the quantity obtained issmall and upon refining the product does not prove satisfactory. In theplants operating on resinous woods for the manufacture of wood pulp,resin con-' taining black liquor has only fuel value in the black ashfurnace used to decompose the sodium sulphate into sodium carbonate andsodium sulphid.

The object of this invention therefore is 40 an improved and economicalmethod of recovering the resinous content of such pulping liquor,especially that resulting from the sulphate or soda process, in a formanda quality equalling, ifnot superior to, that obtained directly fromthe crude resin gum.

My invention is particularly productive in treating the liquor obtainedfrom the stumpage of the long leaf pine which conta ns 400 to 700 poundsof rosin to the cord, but its I employment is profitable in thetreatment of liquors obtained from the pulping of woods a smallercontent of rosin.

The chemical formula of the abietic acid is given by some authorities as0 11 0, and

$ by others as C H O thus'signifying a molecular weight of approximately302 and 288 respectively.

In the sulphate process of manufactur-v mg pulp the usual source of thealkali employed is derived from salt cake (sodium sulphate Na SO,) whichafter passing through the black "ash furnace in the presence of organicmatter is changed to sodium car bonate and sodium sulphid as beforeindicated. Therefore assuming, as an example, that the rosin content ofa cord of wood is 500 pounds there will be required about 100 to 125poliinds of salt cake to produce the amount of sodium hydroxid orsulphid necessary to neutralize the abietic acid content of the resinousmatter of such wood. The sodium resinate contained in the spent pulpliquor is soluble in the liquor.

In carrying out my process I add sufiicient n1tre cake (sodium acidsulphate NaHSOQ to the black liquor above referred to and according toits alkalinity and -rosin content to precipitate all the rosin from thesodium resinate this reaction being accompanied by released andprecipitated ligneous acids. Nitre cake, being sodium acid sulphate, isconsidered herein on account of its acid properties as constitutingpresent purposes an acid. Instead. of nitre cake, sulphuric acid orother suitable acid may be employed. By this means the combined sodiumof the resinate and wood acids are changed into sulphates which inpassing through the standard black ash furnace are again converted intothe sodium sulphid and sodium carbonate both of which may be again usedfor pulpmg. From this processthere results an additional quantity ofsodium sulphate due to the use of the nitre cake, such additionalquantity amounting to about 50 per cent of the cake used. By my processtherefore 1 simultaneously secure two valuable results. namely: recoveryof rosin from the spent pulping liquor and the sodium sulphate at verylow cost. The amount of nitre cake needed for complete precipitationshould be determined in each batch of spent liquor by analyzing it foralkalinity and sodium resinate by the standard methods of analysis forrosin. content, because the resinous content of wood varies according tothe variety of wood used as well as according to the part of the tree'from which it comes.

In the black ash furnace, above mentioned, which is used for the purposeof converting the sodium sulphate into sodium sulphide and sodiumcarbonate, thereaction taking place forms sulphur dioxid which goes intothe atmosphere as an objectionable fume. Should nitre cake beunavailable at commercial costs I pass the gases formed in the furnacethrough the black liquor to avoid the expense of sulphuric acid, thesulphur dioxid createdwhen the sodium sulphate is heated in the presenceof organic matter forming sulphurous acid with the water present whichprecipitates'the rosin from thesodium resinate in the same manner astakes place when nitre cake or sulphuric acid is used. This procedurenot only precipitates the rosin and Wood acids but at the same timeeliminates the objectionable fumes referred to.

In the acompanying drawings Figure 1 is a plan view of the apparatusemployed in carrying out the present invention.

Fig. 2 is a side elevation thereof; and

Fig. 3 is a vertical sectional view of the tank employed in theseparation of the resin from the black liquor.

One convenient method for carrying out the first step of my process,that is; the converting of the soluble sodium resinate in the blackliquor into resin, is shown in the accompanying drawings in which Fig.1, A, A and A are tanks which permit of the treatment of the blackliquor for the purpose of liberating the rosin from the sodium resinate.Fig. 3 is a cross section of any of the tanks A, A and A. At the upperpart of the tanks A, A and A in a circular trough or colander having theupper part perforated and within this colander are the steam coils 5.The colander is provided with the rosin outlet trough 6. Suspended inthe center of the top of the tanks A, A, and A, are the conicaldeflectors 7. Immediately below the colander is the black liquor outlet8, having the valve 9 for regulation purposes. Near the bottom of thetanks A, A and A are the perforated coils 10.

To carry out this first step of the operation, the black liquor is fedintothe tank A through the feed line 1, the flow being regulated by thevalve 2. After the tank has been filled to a point above the outlet 8,the valve 9 is regulated so that the height of the liquor is below theopenings in the side of the colander. Acid in a gaseous form as thatfrom the black ash furnaces as described above, containing sulphurdioxid, or from other suitable source is pumped through the perforatedcoil 10 thereby immediately liberating the rosin from the sodiumresinate causing 1t to rise immediately to the top of the I liquid.

The next step in my process is to separate the precipitate from theliquor described which I do by decantation or filterin This decantationis aided by the conical deflector eeaqse 7 shown in Fig. 3, the impurerosin being carried'into the trough 6 by means of the colander heated bythe steam coils 5 and hence into the solvent tanks B and B. Theprecipitate.

which contains many impurities such as wood acids and other ligneousmatter, is then digested at atmospheric pressure with an organic solventsuch as benzol, gasoline, toluol or kerosene in quantity sufficient todissolve the resin and rosin oils. This dissolving of the rosin androsin oils can be carried out at ordinary temperatures by means of theagitator 12, Fig. 1. After dissolving has been accomplished the agitatoris stopped-and the dissolved rosin ready for distillation.

The solution of resinous bodies resulting from this digestion is thendistilled under a reduced pressure and when carried out in a glassapparatus with about 4 cm. mercury pressure, it can be distilled overwith the rosin practically undeeomposcd, but in iron stills it isdiilicult to prevent some decomposition of the resin into a hydrocarbonvariously known as colophene or abietene and which is the resultantproduced when the carboxyl group of the rosin acid has been eliminated.-

Because of the decomposition which takes place when the pressure-isincreased or in the presence of metals, it is advisable in thedistilling operation in a metallic still referred to, to still furtherreduce the boiling point of the rosin by first preheating the solutionof rosin and atomizing the mixture by means of pressure on the liquid,forcing it through a spray or atomizing nozzle into a vacuumized chamberand condensing fractio nally both the organic solvent and the resincontained therein, the vapor from the organic solvent thus servingsufficiently to reduce the boiling point of therosin itself andtherefore prevent its decomposition. The resultant crystallizable rosindistillate is then filter pressed from any oils condensed with it andthen heated to put into melted form. In this manner a very pure resin isobtained free from objectionable impurities.

By referring to Fig. 1 and Fig. 2 of the drawings it can be seen howthis step can be carried out. The solution of rosin in gasoline in thesolvent tanks B and B is pumped by the pump 13 through the line 15 topreheater 29 where it is heated and thence to the pressure tank 16. Herea pressure is maintained suiiiciently high to atomize the resin mixtureinto the stills D, D and -D which are equipped With condensers E, E andE" and'distillate receiving tanks F to F A high vacuum is maintained byvacuum pump 17 which is connected through condenser G.

In case rosin itself is to be produced and not sodium resinate, thencondensers E, E and E" are maintained sufficiently hot by the absence ofcooling water to maintain the solvent in gaseous form but suflicientlycool to condense the rosin. The steam coil 18 is provided for thepurpose ceiving tanks F to F at a. temperature to prevent thecondensation of the solvent, which passes to condenser G and is therecondensed and tapped oil for further use. The rosin is drawn oil throughthe valve 26.

It is well known that from 35% to 40% of the rosin produced inthiscountry enters into the manufacture of rosin soap and for thispurpose the rosin acids are neutralized or saponiiied with soda. ash orcaustic soda. I have discovered that the rosin in the organic solutionaforementioned either before or after distillation may be recovered fromthe solution by adding an aqueous solution of an alkali t0 the rosinsolution and agitating the mixture thereby neutralizing the abietic acidwhich will separate out first as an emulsion but later on standing itwill break down so that it will be in solution in the water thusseparating the organic solvent which will form a distinct layer on thetop that can be decanted to be ,again used to dissolve succeedingbatches. The solution of sodium resinate in water is then evaporatedleaving the granular sodium resinate as a. residue useful inmanufacturing soap or paper size.

WVhen sodium resinate is to be manufactured the entire distillate iscondensed in the condensers E, E and E and collected in the receivingtanks F to F. The condensed material is pumped by means of pump 23 totank H equipped with agitator 24 condenser I and pump 25 for the purposeof neutralization for resinate production, this procedure being setforth in patent application Serial No.

17 2,821, filed March 4, 1927, in continuation in part.

The amount of caustic soda used to completely precipitate the abieticacid from its solution in the solvent is determined by titrating a knownamount of the solution dissolved in alcohol and ether with a standardalkali solution.

Atomizing pressures depend on the spray nozzle used, these can be workedunder pres sures from 10 pounds up, depending on volume and type ofnozzle used. The temperature of distillation is dependent on thesolventused and a good grade of kerosene and an absolute pressure ofabout 4 cm. of mercury, the temperature range in the liquid will runaround 240 degrees centigrade providing two parts of solvent is used toone of the rosin.

' What I claim is:

1. A process of recovering rosin from liqof maintaining the rethe vacuumobtaintable, with uors obtained by the alkaline treatment of resinouswood consisting .in liberating impure rosin from the alkaline llquors bypassing an acid gas through said liquor, removing said liberated rosinfrom said liquor, dissolving'the removed impure rosin in a hydrocarbonsolvent, distilling the solution of rosin and solvent under a highvacuum, condensing and separating'the rosin from the solvent.

2. A process of recovering rosin from liquors obtained by the alkalinetreatment of resinous wood consisting in liberating impure rosin fromthe alkaline liquors by passing sulphur dioxid gas through said liquor,removing said liberated rosinufrom said liquor, dissolving the removedimpure rosin in a hydrocarbon solvent, distilling the solution of rosinand solvent under a high vacuum, condensing and separating solvent.

3. In a process of obtaining rosin from the resinates contained in.alkaline pulping liquors in which the resinate is decomposed the rosinfrom the' by a'mineral acid forming rosin which has resinate isdecomposed by a mineral acid forming rosin which is mixed with an organic solvent, the step of distilling such rosin solvent mixture underhigh vacuum.

5. In a process of obtaining rosin from the resinates from liquorsobtained by the alkaline'treatment of resinous wood in which theresinate is decomposed by a mineralacid forming impure rosin, the stepswhich comprise mixing the said rosin with an organic solvent, distillingthe solution under a. vac-- uum, and separately condensing the solventand rosin whereby the distilled crystallizable rosin is separated fromthe solvent.

6. In a process of producing rosin from the resinates from liquorsobtained by the alkaline treatment of resinous wood in which theresinate has been decomposed by a mineral acid forming rosin whichlatter is mixed with an organic solvent, the step of distilling suchrosin-solvent mixture under a vacuum and 'fractionately separating thedistilled crys tallizable rosin from the solvent and filtering the rosinwhereby very pure rosin, free from Ob ectiOnable impurities, isobtained.

EDWARD H. FRENCH.

Hill

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